A variety of systems are available for mounting an engine/transmission power plant to vehicles. The primary function of the mounting is to transfer force and torque developed in the engine/transmission to wheels on the vehicle.
In vehicles such as automobiles and heavy trucks, it is desirable that the mounting systems also perform a dampening function which dampens vibrations generated in the engine/transmission so that the passengers and/or driver are isolated therefrom.
Automobile engines are typically connected to automobile transmissions. These transmissions have relatively low gear ratios and generate relatively low torque. Thus, unitary mounting systems which both react torque generated by the engine/transmission pair against the vehicle and dampen vibrations caused by the internal-combustion engine can be used. The mounting system described in U.S. Pat. No. 1,752,809, issued to Riordan, and the system disclosed in U.S. Pat. No. 1,918,490, issued to Riley, are typical of such systems. In other automobile power plant mounting systems, engine vibrations are absorbed in torque-free mountings, and torque generated by the engine/transmission pair is transferred to a vehicle axle as shown in U.S. Pat. No. 1,976,701, issued to Trott.
Large trucks present mounting problems different from those encountered by automobiles. Specifically, truck transmissions have relatively large gear ratios which generate substantial torque. Unitary mounting systems which are intended to both react torque generated by the engine/transmission pair and dampen vibrations generated by the engine are unsatisfactory. If the system is made stiff enough to adequately react substantial torque generated by the engine and transmission, the engine mountings will be too stiff to effectively dampen engine vibrations. Furthermore, transmitting torque to one vehicle axle, as shown by Trott, disadvantageously interferes with operation of the axle suspension.
Therefore, a need exists for an engine and transmission mounting system which satisfactorily reacts engine and transmission torque against a vehicle frame and which also provides a relatively soft mounting for absorbing engine vibrations.